For elderly people and patients with disease or before and after surgery who cannot take food orally, a tube feeding method is used for nutritional support. The tube feeding method includes a method of administering intravenously nutrition and a method of administering enterally nutrition into the alimentary canal. It is believed that the enteral nutrition is desirably used when the administration to the alimentary canal can be performed because, for example, the enteral nutrition does not require strict aseptic handling and bowel function can be maintained as compared with the intravenous administration. In the enteral nutrition, the administration is often performed through a nasogastric tube, a gastrostomy tube, or the like. For such an administration, liquid nutrition foods are typically used. However, it is known that the use of the liquid nutrition food may cause gastroesophageal reflux disease, aspiration pneumonia, diarrheal disease, leakage from a fistula, or the like because the nutrition food is a liquid. As a measure of such a problem, there are reports that semi-solidification of a nutrition food or a nutrition food having a higher viscosity is effective. However, such measures can not sufficiently solve the problems because, for example, such a food needs a certain amount of time for preparation or a certain amount of force that continues to be applied for pushing out the nutrition food during tube feeding.
As means for solving these problems, there are disclosed, for example, a gelling agent containing a gellan gum and alginic acid and a tube feeding nutrition food containing the gelling agent (Patent Document 1) as well as an enteral nutrient using carrageenan in sodium form as a semi-solidifying agent (Patent Document 2). These inventions intend to prevent the problems by adding, to a liquid food, the gellan gum, the carrageenan, or the like for gelation (semi-solidification) of the liquid food. These gelation techniques for liquid foods are considered to be also effective for the relief of the feeling of hunger, the suppression of sudden increase in blood glucose level, and the like and inventions relating to the applications of such a technique to a diet food and a food for diabetes are also disclosed (Patent Documents 3 to 5).
However, it is supposed that there is still room for improvement in these conventional gelation techniques for liquid foods from the viewpoints of the change in physical properties due to dilution of food, easiness in food intake, stability of food during storage, a nutritional viewpoint of food, and the like. For example, in the tube feeding nutrition food disclosed in Patent Document 1, a gelling agent simultaneously containing a gellan gum and alginic acid is added to a tube feeding nutrition food. However, after the gelling agent is added to the tube feeding nutrition food, water is required to be further added, and such preparation takes some time and effort. In addition, the food after preparation is diluted by the amount of the gelling agent added and hence may have greatly altered physical properties from those of the original tube feeding nutrition food. In Patent Document 2, carrageenan is added to a food as a semi-solidifying agent, and the food is semi-solidified in a short period after preparation. Thus, even when a prepared food has flowability capable of tube feeding, it requires a certain amount of force for passing through a tube because it has a high viscosity and may cause tube clogging. Hence, such a food is not necessarily easily taken. Furthermore, in these techniques (Patent Documents 1 and 2), when the gelling agent or the semi-solidifying agent is preliminarily mixed in a food, the food is solidified with time. Thus, the gelling agent such as a water-soluble dietary fiber is added to a food immediately before intake. Therefore, the techniques are a technique in which two liquids are mixed for use and do not provide a one-pack type product in which a gelling agent is preliminarily mixed in a food.
Patent Document 3 discloses a technique relating to a diet food and a food for diabetes utilizing that a simple composition composed of alginic acid and a calcium compound insoluble in a neutral condition changes into a gel when the composition is in contact with gastric juice. However, the water-soluble dietary fiber such as alginic acid may cause component separation such as phase separation when such a fiber is mixed with protein. No protein is actually mixed in Patent Document 3. The technique in Patent Document 3 is a technique for providing a diet food and a food for diabetes. There is no description relating to a method for adding mineral components other than a calcium compound and the effect is not studied. However, mineral components other than a calcium compound are important mineral components for humans and a composition without mineral components other than the calcium compound is not a nutritionally satisfactory composition. Furthermore, the technique disclosed in Patent Document 3 may cause problems. For example, in the preparation of an enteral nutrition food that is taken by, for example, elderly people and patients with disease or before and after surgery who cannot take food orally or of a nutrition food containing many components such as protein and mineral components, physical properties may be impaired during preparation or storage and nutrient components may be separated during storage.
Patent Document 4 relates to a composition that is liquid at around neutral pH and that forms an adhesive matrix at low pH. The composition includes (a) at least 0.05 wt % of pectin having a degree of methoxylation of 2 to 50 and/or of alginate, (b) at least 5 mg of calcium per 100 ml, and (c) at least 0.1 wt % of indigestible oligosaccharide having a degree of polymerization of 2 to 60 as essential components and includes digestible carbohydrates, lipids, and plant proteins such as a soybean as optional components. Patent Document 5 relates to a food composition having enhanced satiety effect. The food composition includes at least 1 wt % of protein and 0.1 to 5 wt % of a biopolymer thickening agent (for example, pectin and alginate) that is not denatured or hydrolyzed between pH 2 and 4 as essential components. The food compositions described in these patents have an effect of obtaining higher viscosity in the stomach to enhance satiety effect. However, the present inventors have studied to reveal that a food composition prepared by mixing raw materials described in these patents causes problems of generating aggregates during preparation and/or storage. When such aggregates have been generated, tube feeding of the prepared composition has caused a problem of tube clogging due to the aggregates present in the liquid food composition (especially a throttle for controlling feeding speed has been clogged with the aggregates). Furthermore, the liquid food composition has obtained a high viscosity due to the presence of the aggregates to result in poor tube passage performance of the liquid food composition. Moreover, for oral intake of the prepared composition, the presence of the aggregates has increased “granular texture” and the presence of the aggregates has increased the viscosity to greatly impair “swallowing feeling”. Therefore, the conventional liquid food composition that is semi-solidified in an acidic region has been very difficult to be used.